TO CORRESPONDENTS. 



In reply to " Barnacles," we inform him that the Right Ascension 

 and Declination of all the principal stars (nearly 3000 in number) are given 

 in the Catalogue of the Astronomical Society : but we do not know of 

 any work that contains the " Distances" of the stars. 



In our next Number we hope to give Dr. Schmidt's Paper on the 

 Dimensions of the Earth ; the Rev. Mr. Vernon's Examination of Cry- 

 stallized Oxide of Zinc ; Mr. Alison's Narrative of an Ascent to the 

 Summit of the Peak of Teneriffe; and Mr. W. Herapath's Paper. 



Mr. J. Prideaux's Paper and Correction have been received, and will 

 meet with early attention. 



*^i,* The Editors request that all Communications intendedjbr immediate 

 insertion vmy be sent to the care of Mr. Richard Taylor, Printing Offiee, 

 Red Lion Court, Fleet Street, London, at Jurthest by the 15ik day of the 

 month, or they will be too late to appear in the ensuing Number. 



PHILOSOPHICAL INSTRUMENTS. 



ANEW AND ENLARGED DESCRIPTIVE CATALOGUE (with 

 the Price of each Article specified ) has been recently published by 

 Watkins and Hill, 5 Charing-Cross. May be had of all Booksellers, 

 price \s. 



Also just published, in 8vo, with Plates, S;. bds. 



A POPULAR SKETCH of ELECTRO-MAGNETISM, or ELEC- 

 TRO-DYNAMICS, with Outlines of the Parent Sciences, Electricity 

 and Magnetism, 



By FRANCIS WATKINS, 

 Curator of Philosophical Apparatus in the University of London. 



Printed, for John Taylor, Bookseller and Publisher to the London Uni- 

 versity, 30 Upper Gower-street; Deightons, Cambridge; Parker, Ox- 

 ford ; and Watkins and Hill, Philosophical Instrument Makers, Charing- 

 Cross. 



" The prefatory outlines of Electricity and Magnetism are drawn up in 

 a satisfactory manner ; and the sketch of Electro-magnetism itself, gives 

 a clear and connected detail of the principal observations and results of 

 experiment, of which the science at present consists, with an account of 

 the various experiments themselves, and directions for their performance." 

 — Phil, Mag. and Annals of Philosophy. 



